1. Field of the Invention
The present invention relates to a navigation apparatus, which carries out an indication display of a present position, an advance course, etc, to support a driving operation of a movable body, such as a car. Especially, the present invention relates to a navigation apparatus, to which a destination position is firstly set and inputted, and which obtains an optimum movement course on the basis of map information inputted beforehand to display the course to guide.
2. Description of the Related Art
In a navigation apparatus mounted in a vehicle etc., it is demanded to measure a present position and an advance direction of the self-vehicle precisely, display map information corresponding to the present position of the self-vehicle precisely and rapidly by a display device etc., one after another, and provide a driver with a course from the present position to the destination position.
The navigation apparatus mounted in a vehicle or car etc., selects a course, which has an azimuth closest to the azimuth from the present position to the destination position of the self-vehicle, by use of position information as for the inputted destination position and various courses to the destination position from the present position, so that the navigation apparatus displays the advance course to guide from the present position to the destination position.
FIG. 11 indicates an example of a course searching operation in case of using such a navigation apparatus. In FIG. 11, the reference numeral S represents a present position, the reference numeral D represents a destination position, and the numbers 1 to 6 represent crossings through which the self-vehicle are guided to pass respectively. In case of the navigation apparatus, which selects the course having the azimuth closest to the azimuth from the present position of the self-vehicle to the destination position, when the destination position D is inputted thereto, the navigation apparatus displays such a course to guide that the self-vehicle advances straight from the present position S to the crossing 3, turns to the right at the crossing 3, turns to the left at the crossing 4, turns to the right at the crossing 5 and turns to the left at the crossing 6, so as to reach the destination position D. In this manner, the navigation apparatus is constructed to support the driving operation.
However, in case of searching a course shown in FIG. 12 by use of such a navigation apparatus, since a course does not exist between the present position S and the destination position D, an infinite loop is generated such that the course to the destination position D may be unable to be found out. Namely, in FIG. 12, if the destination position D is inputted at the present position S, the self-vehicle advances straight from the present position S to the crossing 3, makes a U-turn at the crossing 3, and advances straight to the crossing 1. Therefore, the navigation apparatus displays such a movement course to guide that the self-vehicle takes a round trip between the crossing 1 and the crossing 3 henceforth. In this case, by setting, as a prohibition position, a position in case that the self-vehicle reaches the end point of data, or a position in case that all advancing directions of the self-vehicle are surrounded by the points where the self-vehicle has passed once in the search, and by giving a process to return the self-vehicle to one previous position without going to the prohibited position, it may be possible to overcome the above mentioned problem.
However, in this case, many courses should be searched until it reaches to the destination position D, as shown in FIG. 13, so that the process becomes complicated and a long searching time becomes necessary.